1. Field of the Invention
The present invention relates to an inertial driving actuator.
2. Description of the Related Art
Assume that a driving pulse with a waveform having a moderate rise and a subsequent sharp decay is applied to a piezoelectric element as a kind of electromechanical converting element. The piezoelectric element moderately extends at the moderate rise of the driving pulse, and quickly contracts at its sharp decay. An inertial driving actuator that utilizes these characteristics is known. In the inertial driving actuator, a driving pulse having the above waveform is applied to a piezoelectric element to generate oscillations having different speeds in the extending and contracting directions. This reciprocally moves a driving member fixed to the piezoelectric element at different speeds. Thus, a moving member frictionally coupled to the driving member moves in a predetermined direction.
Jpn. Pat. Appln. KOKAI Publication No. 2003-185406 discloses an inertial driving actuator with a position detection function for a moving member. FIG. 10 shows this inertial driving actuator. In this inertial driving actuator 100, one end of a piezoelectric element 120 is fixed to a frame 110 of the actuator by means such as adhesion. A driving shaft 130 is fixed to the other end of the piezoelectric element 120 by means such as adhesion. A moving member 140 is frictionally coupled to the driving shaft 130. A detection member 150 constitutes a fixed electrode to detect the position of the moving member 140 on the basis of an electrostatic capacitance. The detection member 150 extends in parallel to the moving direction of the moving member 140 to be in non-contact with the moving member 140, and is fixed to the frame 110. The driving shaft 130, moving member 140, and detection member 150 are made of a conductive material. The detection member 150 has, on its surface that faces the moving member 140, uneven portions at a predetermined interval in the moving direction of the moving member 140, thus forming an electrode 151. The electrode 151 and moving member 140 face each other at a gap D to form a capacitor.
When assembling the above inertial driving actuator 100, the driving shaft 130 and detection member 150 must be maintained at a gap and a parallel degree respectively falling within allowable ranges. This is because in position detection utilizing an electrostatic capacitance, a change in gap between electrodes that form a capacitor may decrease the detection accuracy.